The invention relates to a fastener, in particular for securing a gas bag module to a steering wheel, the fastener comprising two fastening arms and a fastener part.
Securing the gas bag module, containing the drivers air bag, to a steering wheel needs to satisfy various requirements. For one thing it needs to be rugged enough so that it will under no circumstances become loose during deployment of the gas bag in a restraint situation, but for another, it needs to be releasable for any repair or replacement of the gas bag module needed. Apart from this the time it takes in installing the gas bag module should be a minimum. These requirements can be satisfied by snap-action fasteners in which flexible arms engage protuberances provided on a companion piece. The disadvantage with known snap-action fasteners is that they can only be released with difficulty, or, if easily releasable are not rugged enough.
The object of the invention is to propose a fastener ensuring a safe but readily releasable connection of two components, more particularly of a gas bag module and a steering wheel.
This is achieved in a fastener which comprises two fastening arms and a fastener part. The fastening arms enter into a snap-action connection with the fastener part and clasp the fastener part in a connected condition. Due to the double-sided engagement a firm connection materializes between the fastening arms and the fastener part. The connection is easily released by pressing apart the arms with a suitable tool, it being of advantage that releasing the connection is no-destructive. Since the fastening arms are pretensioned inwards the risk of the arms being damaged is reduced.
In one preferred embodiment of the invention the fastening arms are provided with hooks having contact surface areas and the fastener part comprises a concave contacting surface area into which the contact surface areas of the hooks engage in the connected condition. This design improves retainment of the hooks on the fastener part. In addition to this the concave contacting surface area of the fastener part serves to guide the contact surface areas of the hooks during release of the connection.
In another preferred embodiment the fastener part and the fastening arms comprise ramps corresponding to each other. These ramps form guides which reduce the loading of the fastening arms on spreading and prevent damage to the snap-action hooks in producing the connection.
Preferably the ramps are configured on the fastener part such that they form an angle and that the fastening arms slide back towards the apex of the angle should the connection fail to be made. This configuration ensures that a component provided with fastening arms, more particularly a gas bag module which to produce the connection is inserted into a component containing the fastener part, more particularly a steering wheel, is urged back should the snap-action connection fail to latch, thus making it easy to recognize faulty assembly. This movement may be supported by a spring.
Advantageously an assembly comprising a steering wheel and a gas bag module is provided, the fastening arms being connected to the gas bag module and the fastener part to the steering wheel in order to improve access to the fastener. Preferably in this arrangement the fastening arms are configured integrally with the gas bag module, e.g. in the region of the inflator mount or generally a module supporting structure, and the fastener part is configured integrally with the steering wheel, e.g. with its supporting structure. In this way there is achieved a rugged configuration whilst simultaneously reducing the number of components required since the fastener part and the fastening arms, respectively, do not need to be produced as separate elements.